This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. The goal of this study is to elucidate the molecular signaling and mechanism of mitotic telomere DNA damage response and repair of DSBs in eukaryotes, and to determine which damage recognition factors, and repair proteins are recruited at mitotic telomeres when localized DSBs are produced with a near infra-red (NIR) femtosecond laser (800 nm). We hypothesized that mitotic telomere DNA damage signaling and repair factors are present in mitosis, thus mitotic telomeres undergo DNA repair. Using a NIR laser to create DSBs on mitotic telomeres of human and marsupial cells (Potorous tridactylus PtK1), and immunostaining, we observed the recruitment of an induced foci of DSB damage recognition factors and repair proteins such as [unreadable]H2AX, NBS1, ATM-Ser1981P, Ku70/80 and TRF2-Thr188P at the site of NIR laser-induced telomere damage. This project can be improved with the help of confocal microscope. Confocal analysis of fluorescent antibodies will be more specific and with a better resolution. These results will provide information about the accessibility of damaging agents and repair processes in telomeric DNA, thus contributing to a better understanding of aging and cancer.